1. Field of the Invention.
The present invention relates to a universal power supply unit for different small electrical appliances and consists of an energy station with an integrated voltage source and a downstream voltage converter associated with a given small appliance, for supplying an output voltage and an output current and of a standard adapter cable with an appliance-specific connector plug for transmitting the available output power to a given small appliance.
2. The Prior Art.
Compact small electrical appliances of high technical utility are being increasingly used in households, industry and while traveling. Among these, the largest segment are mobile appliances from the fields of telecommunications, data processing and audio; mobile telephones, palmtop computers or portable CD-players may be mentioned as typical examples. One characteristic of such devices is that for the sake of reduced weight and more compact dimensions they have no power packs. Instead, there usually is provided a battery receptacle for batteries which are replaceable by a user and/or a connector for supplying external power. In many cases, for instance in mobile telephones, a mains adapter is commonly furnished with the device for charging removable batteries and for simultaneously supplying power to the appliance.
Aside from the mains-powered appliances, other possibilities for energizing small appliances also exist. For instance, automotive charge cables are available for mobile telephones which in the simplest cause a drop in voltage by means of diodes and thus reduce the automobile voltage of 12 V by generating heat, to the lower charge voltage of the mobile telephone. In technically more sophisticated versions a switch transducer is provided in such a cable making the described adjustment with a high degree of efficiency. Such versions lead, however, to a significant increase in the dimensions of the cable since they require integration of a complete circuit including housing. As disclosed by German Patent specification DE 197 56 626, the NOKIA 1611 Solar or by a paper of the Fraunhofer Institut ISE at Freiburg, Germany (see 1998 Annual Report), solar current supply devices have also been proposed or realized in the field of mobile telephones.
Connector plugs containing electronic components are also know in the field of measurement technology: For instance, the Ahlborn enterprise of Holzkirchen, Germany, is marketing a sensor system called xe2x80x9cALMEMOxe2x80x9d in which sensor circuits are integrated in special connector plugs, thus reducing internal interferences. In German patent application No. DE 195 27 972, a measuring resistor integrated in the end of a cable detects ruptures in water pipes. The possibility of externally controlling power supplies by removal of voltage setting or current limiting components is also known in the art.
In the mentioned supply devices the external current supply is usually designed to accommodate a certain related small appliance. This excludes the universal application of such current supply devices in connection with other small appliances provided with different connectors or requiring different feed voltages. Consequently, a large number of supply devices are used in connection with small appliances of similar power characteristics which, in principle, could be energized by a single adaptable supply apparatus.
Universal current supply devices for small appliances of different feed voltages and connectors have been known for a long time. For instance, power adapters with output voltages of from 3 to 12 V are available with a set of 4 to 6 common low power plugs and equipped with a switch for selecting the output voltage. They are suitable for operation with many audio devices as well as portable computers. Also, chargers are known in the field of solar current supplies which are provided with a plug-in cable and multiple plug adapter (see Conrad Catalog ""98, e.g. xe2x80x9cSito Solar Chargerxe2x80x9d). They are suitable for feeding appliances of 3 V feed voltages. Other solar current supply devices are also capable of furnishing different output voltages by means of switches mounted on the supply device (see German utility model U 188 01 229 or xe2x80x9cSunline Solarkofferxe2x80x9d in Conrad Catalog, ""99, page 323).
The state of the art upon which the invention is based is described in the pamphlet Solarcxe2x80x94innovative Solarproduktexe2x80x94Variante 3: CSM9.040A02Txe2x80x9d of the Solarc enterprise, state 09/98. It describes a universal energy station of credit card format consisting of a combination of a battery charge module and a voltage converter module. These modules are furnished for individual output voltages and connector cables which may be adapted to predetermined small appliances by the factory or by skilled users. The output voltage is set in the circuit of the energy station by a single component disposed in the negative feedback branch of a switching transducer. Upward and downward transformations of voltages are made possible with a high degree of efficiency by such switching transducers.
However, the described as well as other mentioned universal current supply devices suffer from three grave characteristics which make operating specific small appliances, such as, for instance, modern mobile telephones all but impossible for an average user. Firstly, with most small appliances their manufacturer does not reveal level and flow of the required feed voltage and of the feed current. Secondly, a user who is not technically astute cannot be expected to adjust the feed voltage and even, in some cases, the maximum current. Thirdly, the very specific connector plugs are often exclusively designed for one type of apparatus, and they are not commercially available either as accessories for universal power supply devices or individually.
The technical task of the invention, therefore, resides in providing a universal and compact energy supply unit which makes possible an uncomplicated and, at the same time, cost-efficient adaptation to many different small electrical appliances, yet allows simple utilization without adjustments such as, for instance, the selection of feed voltages. The module is also to be robust and practical. For some applications, the device is to be constituted as an autarchic energy apparatus, for instance as a solar module for energizing mobile telephones and audio devices while traveling. Such a version, in particular, requires a circuit arrangement with power losses as low as possible.
The task is accomplished by the invention by the provision in the appliance-specific adapter cable of a group of electronic components for generating an individual programming signal which when coupling the adapter cable to an energy station is detected by a switch control unit at the voltage converter and is correspondingly converted by the voltage converter to set the required output power.
By dividing the power supply unit in accordance with the invention into a technically more elaborate energy station as the core unit and an uncomplicated peripheral part as an exchangeable component, all the requirements mentioned are attained: The application of the switching or voltage converter in the energy station results in a compact structure and to high degrees of efficiency; the design of the adapter cable with but a few structural components makes possible a low-cost adaptation to many small appliances. For the user, this entails a very simple operation. All he needs are the adapter cables fitting his small appliances. Adjustments of the energy station are completely eliminated. The output power required for a given small appliance is set automatically simply by connecting the appropriate adapter cable. Since any adjustment choices have been eliminated no mismatching can occur. The correct association of the adapter cables with the small appliances is accomplished by the appliance-specific output plug of the cables.
In order to recognize the programming signals generated by the adapter cable, the voltage converter in the energy station is provided with a detector switch control unit such as, for instance, a voltage detector. To activate the detector, it is advantageous, in accordance with one embodiment of the invention, to provide a resistor bridge in the component group of the adapter cable. This is a rugged component of small size the dimensions of which may be designed in a simple manner. This is of particular advantage if, in another embodiment, the component group is freely programmable at the energy station as to the setting of the output power. Simple access to the output power to be set is made possible in this manner, for instance by way of electronically programmable logic components. The variegation of the power supply unit in accordance with the invention may thus be improved further.
In accordance with a further embodiment of the invention, programming of physical parameters affecting the power supply may be taken into consideration, in addition to the programming of the feed voltage. In this manner, the behavior of the energy station may be influenced by the use of programmable adapter cables. A pulsating voltage may be set instead of a constant one. The available current may be limited to a maximum value. The voltage converter may be activated by insertion of the connector cable and otherwise remain in a current-saving mode. The output voltage may be varied as a function of certain physical ambient conditions such as, for instance, temperature, pressure or brightness.
In accordance with a further embodiment of the invention, the integrated voltage source of the universal power supply unit will, in the simplest case, be energized by mains power. Where it is provided with an integrated mains power device, the power supply unit may be designed as a mains plug-in device. In particular, a mains power switching component may be utilized in this connection for yielding a high degree of efficiency, low idle current and small dimensions. However, with an integrated mains power device, the energy supply station becomes relatively immovable. For that reason it is advantageous, in accordance with a further embodiment of the invention, to feed the integrated voltage source from a solar cell array. Where the power supply unit is powered by solar current as a source of direct current, it may either be coupled directly to the direct current converter operating at the optimum operating point of the solar cell array, or it may be buffered by an array of batteries charged by the solar cell array through a suitable charge control.
Occasionally it may happen that the power requirements of a consumer significantly exceed the available power, or that the charge capacity of the battery array needs to be increased. In accordance with a further embodiment of the invention, this may be accomplished by strip connectors provided on the power supply unit for parallel electrical connection of several modules. By connecting several modules by suitable cables a module field may be established the nominal power of which corresponds to the power requirement of the consumer.
If the consumer can be operated by a feed voltage corresponding to the nominal value of the voltage of the direct current source, it may be useful, for connecting an electrical consumer, to provide in the power supply unit a connector for connecting an electrical consumer. In this fashion the power losses of the direct current converter can be avoided.
In accordance with a further embodiment of the invention, a handy portable power supply unit sufficiently powerful for small electrical appliances, such as mobile telephones, portable CD-players and the like, may be fabricated by way of a solar module the basic dimensions of which substantially correspond to the size of a credit card. The solar module may have a housing provided with positioning means for aligning the solar cell array with a source of light. The housing may be structured as a hard shell case, preferably made of plastic, or as a soft housing such as a pouch. A visually appealing and, if desired, luxurious version may consist of a pouch made of soft material, preferably leather.
In accordance with a further embodiment, the positioning means may by a pin the angular disposition of which relative to the housing may be varied for attaching the module to a user""s garment or for setting up the module on a sturdy surface. These means are substantially slip-proof and may include a clasp for affixing the solar module on the garment of a person. Straps and belts for attaching the solar module to an arm or torso may also be useful. Where a clasp is used, it may be structured as a pivotable element pivotable element for obliquely positioning of the solar module on a sturdy surface for a more effective alignment with impinging sun light.
In the context of the present invention the energy station may be mechanically connected or connectable with a structural unit. Such a structural unit which may, for instance, be designed for connection to the connector of the connector cable, may also contain the group of electronic components for generating the programming signal for the energy station. For instance, a solar torch or flashlight may be made by connection of an illumination accessory, or a solar ventilator device may be made by connecting a fan accessory. Moreover, the energy station may be provided with a connector for connecting to an external charger for charging a battery array. When charging the battery array, care must be taken not to overcharge it as damage or a reduced useful life of the battery array may otherwise be expected. For that reason, the electronic control circuit preferably includes a charge control unit for turning off the charge current flowing to the battery array as soon as the battery array has reached a predetermined charge condition. In a simple circuit the charge control unit registers the terminal voltage of the battery array as a measure for its charge condition and switches off the charge current when a predetermined terminal voltage has been reached during a charging operation. In principle, any kind of batteries may be used in the battery array, for example, Nixe2x80x94Cd-accumulators or lithium ion batteries or rechargeable alkaline manganese cells.